Background: Ketamine’s role in the ED has expanded in recent years. The clinical reasons for this make it easy to understand why, and include analgesia, amnesia, and anesthesia. Amazingly, ketamine does not only reduce acute pain, but it also decreases persistent chronic and neuropathic pain as well. More importantly, use of low-dose ketamine (0.1 – 0.3 mg/kg IV) has been demonstrated to be opioid sparing. Some of the major issues with IV push low-dose ketamine include its adverse effects, such as feelings of unreality, nausea/vomiting, and dizziness. Many emergency medical providers have anecdotally noticed a decrease in adverse effects when ketamine is given slowly. In the paper we are reviewing today, the authors tried to see if increasing the duration of the ketamine from IV push (3 – 5 min) to a slow infusion (10 – 15 min) could mitigate some of these effects, while maintaining analgesic efficacy.

What They Did:

Randomized patients presenting to the ED with acute abdominal, flank, or musculoskeletal pain with an initial pain score of ≥5 to: Ketamine 0.3mg/kg by either IV Push (over 5min) or Short Infusion (0.3mg/kg mixed in 100mL normal saline solution over 15min) with Placebo Double-Dummy (both groups got an iv push, and an infusion).

Limitations:

Small sample size did not allow for assessment of variance in safety profiles of the two routes of administration (i.e. statistical significance) or for possible differences in the other SERSDA assessed adverse effects.

Discussion:

Several studies have shown a correlation to side effects of low-dose ketamine with rapid rates of infusion. The pharmacologic reason for this is ketamine’s lipophilicity allows for rapid penetration of the blood-brain barrier and rapid saturation of the NMDA/glutamate receptors.

Excluded head / eye injured patients despite ample evidence that ketamine is safe in these populations.

The authors note that in their institution a 15 min infusion is billed the same as an IV push.

One issue with slow infusion would be the availability of an infusion pump, however the authors discuss hanging the infusion, and running over approximately 15 min, without using an infusion pump. This saves time setting up the pump, and saves the issue of running out of pumps. We emailed the lead author Sergey Motov about this and his response was as follows:

“In my ED, we do not routinely use an IV infusion pump for a short infusion of SDK. After 6 years of doing so we have had no major adverse effects. Our nurses and ED pharmacists are very comfortable with a no pump approach by adjusting the flow rate to a 15 min time frame. Furthermore, we cap the max dose at 30 mg even if patient’s weight exceeds 100 kg which adds additional safety/comfort to our staff. This only applies to short infusion. For continuous drips we use IV infusion pumps. ”

Author Conclusion: “Low-dose ketamine given as a short infusion is associated with significantly lower rates of feeling of unreality and sedation with no difference in analgesic efficacy in comparison to intravenous push.”

Clinical Take Home Point: Low dose ketamine of 0.3mg/kg, mixed into 100mL of Normal Saline given over slow infusion (15 minutes) has a decreased side effect (i.e hallucinations or dizziness) and equal analgesic profile when compared to IV push (5 minutes) low dose ketamine.